Field of the Invention
The invention relates to biodegradable and nutritionally attractive composition comprising biocidal or antibiotic compounds and/or microbes having bio-adhesion and controlled buoyancy properties for selectively fed to an aquatic organism in open or close water-bodies, and bioactive components are released upon contact with mucosal tissues such as gill, skin or along the digestive tract of the selected aquatic organism.
Description of the Related Art
Non-indigenous aquatic species are rapidly spreading worldwide, causing both a severe loss of global biodiversity and environmental and economic damages [1, 2, 3]. In addition to direct effects on habitat quality, the expected climate changes will foster the expansion of invasive species into new areas and magnify the effects already present by altering competitive dominance, increasing predation and infectious diseases. Aquatic species that are considered invasive are non-native species, as they are free from natural predators, reproduce rapidly and aggressively compete with native species. Invasive predatory species prey upon native species and disrupt their aquatic food web. They can affect property values, and influence economies of water-dependent communities.
For example, many non-native aquatic plants, animals and microscopic organisms have been introduced into the Great Lakes since the early 1800s, either accidentally or intentionally. Many of them over-populate the lakes and surrounding rivers. They prey on native fish and plants, and disrupt the ecosystem in the lakes. They also harm the recreational and agricultural activities by damaging boats and gear, underwater cables, oil rig platforms, buoys, fishing nets, clogging water pipes and hydro-power facilities, jamming the fresh water supply chain and choking off irrigation systems in the region. Losses in the U.S. alone are estimated at $78.5 billion annually [4]. Recent efforts across many countries have highlighted the urgent need for more rigorous and comprehensive management programs to prevent and contain the worldwide spread of non-indigenous species.
The invasion of Zebra mussel (Dreissena polymorpha) and Asian clam (Corbicula fluminea) are of particular concern given their ability to rapidly cover the surface of hard submerged substrates, reduce phytoplankton biomass and hence disturb pelagic food webs and act as major macro fouling species of water intake structures and pipes used in municipal, agricultural, industrial, and power station water systems [5, 6]. Asian clams are found in 36 of the contiguous states of the United States as well as in Hawaii. The zebra mussel, introduced into the U.S. in 1986, has spread rapidly throughout the Great Lakes, St. Lawrence River, and waterways associated with the Mississippi River. It is expected that the mussels will, within 20-25 years, infest most areas south of Central Canada and north of the Florida Panhandle from the Pacific Coast to the Atlantic Coast. As the zebra mussel advances, the prognosis for native freshwater bivalve populations is bleak, especially for those populations of species considered threatened and endangered [7].
Another harmful invader is the round goby Neogobius melanostomus, which is one of the most wide-ranging invasive fish on earth. The fish has substantial introduced populations within the Laurentian Great Lakes watershed, the Baltic Sea and several major European rivers. Neogobius melanostomus inhabit a wide range of temperate freshwater and brackish-water ecosystems and without establishing rigorous management programs will probably continue to spread via ballast water, accidental bait release and natural dispersal worldwide [8].
There are many methods of controlling the spread of invasive species. These methods include the mechanical removal such as dredging, chain dragging and hand raking, predator removal, and chemical, biochemical and biological control. It is equally important to manage the invasive species in a safe, environmentally responsible and cost effective manner. For example, in order to find less harmful methods to control invasive mussels, New York State Museum's (NYSM) Field Research Laboratory screened more than 700 bacterial isolates as potential biological control agents against zebra and quagga mussels. As a result, they found a highly effective and lethal strain isolate of Pseudomonas fluorescens (CL145A) against these mussels (U.S. Pat. No. 6,194,194). This harmless bacterium is present in all North American water bodies and even in the average household kitchen and refrigerator [9].
Application of biocides and toxicants is one of the effective ways to reduce a population of invasive species. However, application techniques have not been perfected and as a result those methods have been quite ineffective in eradicating the invasive organism. Another disadvantage is that many toxicants in use such as sodium hypochlorite, surfactants, ammonium salts, N-triphenylmethyl-morpholine have either low toxicity or non-selectively affect the entire water ecosystems. For example, CLAM-TROL pesticide, produced by Betz Chemicals, H130 didecyldimethylammonium chloride produced by Calgon Corp. and 4-trifluoroethyl-4-nitrophenol marketed as BAYLUSCIDE pesticide (Bayer) are acutely toxic to fish and other aquatic organisms and are believed to be quite persistent in the environment [10]. To date, none of those chemical treatments seems likely to replace simple chlorination as the standard treatment for zebra mussels.
The two most widely used fish toxicants in aquatic systems are Rotenone and antimycin A. Rotenone, is a botanical pesticide registered by the EPA for piscicidal (fish kill) uses. The chemical is related to isoflavonoid compounds derived from the roots of Derris spp., Lonchocarpus spp., and Tephrosia spp., and primarily found in Southeast Asia, South America, and East Africa, respectively. Rotenone products are classified as Restricted Use Pesticides (RUP) due to acute inhalation, acute oral, and aquatic toxicity (see EPA 738-R-07-005, March 2007, Registration Eligibility Decision for Rotenone). Rotenone does not dissolve in water. In order to disperse it in water so that it can be effective at low concentrations, rotenone must be formulated with solvents. There are a couple of commercial liquid emulsion products containing rotenone as the active ingredient that can be used for treating aquatic systems. For example, one product is called Nusyn-Noxfish®, the other CFT Legumine®. These piscicides are usually applied by spraying the emulsion on the surface of the water. However, these emulsion-type piscicidal compositions have many disadvantages, as described below.
Antimycin A is a relatively new fish toxicant, and primarily applied as a single management tool. Over the past decade antimycin A has been used by Federal and state agencies to restore threatened/endangered fish to their native habitats (see EPA 738-R-07-007, May 2005, Registration Eligibility Decision for Antimycin A). Antimycin A is also a Restricted Use Pesticide registered by EPA for piscicidal (fish kill) uses. Derived as a fermentation product from Streptomyces mold, the chemical is applied directly to water to renovate recreational fish populations and to remove scaled fish from catfish fingerling and food fish production ponds.
This toxicant is marketed under the trade name of “Fintrol.” Currently, there are three registered formulations of antimycin A available. Fintrol-5 consists of antimycin A coated on sand grains in such a way as to release the toxicant evenly in the first 5 feet of water—as the sand sinks; Fintrol-15 which releases it in the first 15 feet of depth, and a liquid, Fintrol Concentrate, which was developed for use in very shallow running waters and streams. Since its introduction, antimycin A has become an attractive pesticide because of its relative specificity to fish, i.e., the minimal concentrations that kill fish are considered harmless to other aquatic life and mammals. It is effective in very small concentrations against all life stages of fish, egg through adult. Its respiratory inhibiting properties are irreversible at lethal dosages, and as importantly, it rapidly degrades in open environment.
Efforts to better control the release of the toxicant are well known, particularly in the agricultural industry. For example, U.S. Pat. Nos. 3,851,053 and 4,400,374 disclose various polymers with extended diffusion path length. Typically, agents incorporated are organic pesticides, and the matrix type is an elastomer such as natural rubber, styrene-butyl styrene rubber, and the like. It is, however, well known in the art that almost all organic and inorganic pesticidal agents lack solubility in those plastic matrices.
Other known encapsulating systems include; U.S. Pat. Nos. 3,059,379 and 4,428,457 in which a core-granulated fertilizer is encapsulated in porous thin film; U.S. Pat. No. 4,019,890 in which granular fertilizers is coated with a water-resisting layer forming a jelly-like gel coating. U.S. Pat. No. 2,891,355 relates to coating foamed polystyrene particles with a solution of fertilizers and nutrients, adding water, and potting a plant therein. Further, Villamar et al. [11] describes the preparation of complex microcapsules (CXMs) consisting of dietary ingredients and lipid-wall microcapsules (LWMs) embedded in particles of a gelled mixture of alginate and gelatin to obtain a single food-particle type used to provide suspension feeders with dietary nutrients. Other fertilizers such as urea can be coated in a granular form as taught in U.S. Pat. No. 3,336,155, thus retarding solution in ground waters. U.S. Pat. No. 3,276,857 teaches that a fertilizer can be encapsulated with asphalt or various waxes and, thus, emission into the environment is slowed. However, none of this prior art discloses a particle wherein the active agent remains within an intact particle even after exposure in water and wherein it is being released only after consumption by an organism. One approach to deliver a toxicant directly to the invasive species is through conventional aquatic feeds in a dry, semi or wet soft form as a pelleted or flaked feed. These feeds however, rapidly deteriorate in water, with physical decomposition and breakdown of the feed starting immediately with feed delivery into the water. Vulnerable bioactive agents started to leach and decompose when the feed become soaked with water, and potentially harming the surrounding endogenous organisms in the ecosystem.
To overcome some of the disadvantages associated with the delivery in dry pelleted feeds, the active agent has been encapsulated within microcapsules. Several types of natural or synthetic polymers have been proposed for use as a matrix for binding and the controlled release of active agents. Examples of such polymers are poly(vinylpyrrolidone), poly(vinylalcohol), poly(ethylene oxide), cellulose and its derivates, silicone and poly(hydroxyethylmethacrylate). Biodegradable matrices are of interest since the degradation of natural polymers like polysaccharides or starches occurs naturally in the aquatic environment. U.S. Pat. No. 4,239,754 describes a system where a nutritional component such as free amino acids, and hormones are entrapped in a liposome and the liposome is further encapsulated in a hydrocolloid matrix. The resulting lipogel microcapsules were either stored as a freeze-dried powder or suspended in water. This type of liposomal membrane or barrier is fragile, potentially expensive and difficult to make and would not likely remain a discrete microcapsule when combined with other materials, or act as an appropriate part of a desirable aquatic invasive species management program.
The encapsulating polymers described in the art do not solve all of the problems associated with delivering the active agent in the aquatic environment. Production of active agents in liposomes and their subsequent encapsulation in a hydrocolloid matrix is a labor-intensive process that adds to the cost of the final product. Drying the microencapsulated active results in oxidation and deactivation of the active component, and more significantly renders the active agent insoluble and thus not bio-available by the organism. Micro-encapsulated actives that are stored in a dry state still have some of the same disadvantages as described for dry pelleted feeds, as they must still be rehydrated and manually introduced into an aquatic environment. Further, the microencapsulating polymers described in the prior art have not eliminated the decomposition and water leaching problems associated with the use in aquatic environments.
The principle utility of the composition of the present invention lies with its unique controlled buoyancy and bioadhesive matrix, in which the active agent is dispersed in a form of oily droplets. The oil dispersed active agent is enclosed within a particle matrix and will not leach even after extended exposure in water. The bioadhesive polymeric matrix remains intact in the water body wherein mucosal tissues such as gill, skin and digestive tract of the targeted aquatic organism are exploited for uptake and release of the active agent. The method of producing and delivering the composition is economical, environmentally safe and applicable to both freshwater and marine waters. Use of the invention is particularly attractive in controlling major invasive species such as fish, mussel and clam.